[RFC][PATCH 10/10] fs: Convert i_count over to refcount_t

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

Now that i_count is a proper refcount, convert it to refcount_t.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 fs/btrfs/inode.c   |    2 +-
 fs/f2fs/super.c    |    4 ++--
 fs/inode.c         |   16 ++++++++--------
 fs/xfs/xfs_inode.c |    2 +-
 fs/xfs/xfs_inode.h |    2 +-
 include/linux/fs.h |    5 +++--
 kernel/futex.c     |    2 +-
 7 files changed, 17 insertions(+), 16 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3172,7 +3172,7 @@ void btrfs_add_delayed_iput(struct inode
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_inode *binode = BTRFS_I(inode);
 
-	if (atomic_add_unless(&inode->i_count, -1, 2))
+	if (refcount_dec_unless(&inode->i_count, 2))
 		return;
 
 	spin_lock(&fs_info->delayed_iput_lock);
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -601,7 +601,7 @@ static int f2fs_drop_inode(struct inode
 	if ((!inode_unhashed(inode) && inode->i_state & I_SYNC)) {
 		if (!inode->i_nlink && !is_bad_inode(inode)) {
 			/* to avoid evict_inode call simultaneously */
-			atomic_inc(&inode->i_count);
+			refcount_inc(&inode->i_count);
 			spin_unlock(&inode->i_lock);
 
 			/* some remained atomic pages should discarded */
@@ -621,7 +621,7 @@ static int f2fs_drop_inode(struct inode
 
 			fscrypt_put_encryption_info(inode, NULL);
 			spin_lock(&inode->i_lock);
-			atomic_dec(&inode->i_count);
+			refcount_dec(&inode->i_count);
 		}
 		return 0;
 	}
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -135,7 +135,7 @@ int inode_init_always(struct super_block
 	inode->i_sb = sb;
 	inode->i_blkbits = sb->s_blocksize_bits;
 	inode->i_flags = 0;
-	atomic_set(&inode->i_count, 2); /* hashed and ref */
+	refcount_set(&inode->i_count, 2); /* hashed and ref */
 	inode->i_op = &empty_iops;
 	inode->i_fop = &no_open_fops;
 	inode->__i_nlink = 1;
@@ -387,7 +387,7 @@ static void init_once(void *foo)
 void __iget(struct inode *inode)
 {
 	lockdep_assert_held(&inode->i_lock);
-	WARN_ON(!atomic_inc_not_zero(&inode->i_count));
+	refcount_inc(&inode->i_count); /* must not be 0 */
 }
 
 /*
@@ -395,7 +395,7 @@ void __iget(struct inode *inode)
  */
 void ihold(struct inode *inode)
 {
-	WARN_ON(atomic_inc_return(&inode->i_count) < 3);
+	refcount_inc(&inode->i_count);
 }
 EXPORT_SYMBOL(ihold);
 
@@ -818,7 +818,7 @@ static struct inode *find_inode(struct s
 			continue;
 		if (!test(inode, data))
 			continue;
-		if (atomic_inc_not_zero(&inode->i_count))
+		if (refcount_inc_not_zero(&inode->i_count))
 			goto out_unlock;
 		goto slow;
 	}
@@ -875,7 +875,7 @@ static struct inode *find_inode_fast(str
 			continue;
 		if (inode->i_sb != sb)
 			continue;
-		if (atomic_inc_not_zero(&inode->i_count))
+		if (refcount_inc_not_zero(&inode->i_count))
 			goto out_unlock;
 		goto slow;
 	}
@@ -1538,7 +1538,7 @@ void iput(struct inode *inode)
 
 	BUG_ON(inode->i_state & I_CLEAR);
 retry:
-	if (atomic_add_unless(&inode->i_count, -1, 2))
+	if (refcount_dec_unless(&inode->i_count, 2))
 		return;
 
 	spin_lock(&inode->i_lock);
@@ -1551,7 +1551,7 @@ void iput(struct inode *inode)
 		goto retry;
 	}
 
-	atomic_dec(&inode->i_count); /* 2 -> 1 */
+	refcount_dec(&inode->i_count); /* 2 -> 1 */
 	WARN_ON(inode->i_state & I_NEW);
 
 	/*
@@ -1578,7 +1578,7 @@ void iput(struct inode *inode)
 	 * continue to take the inode out, otherwise someone got a ref
 	 * while we weren't looking.
 	 */
-	if (atomic_cmpxchg(&inode->i_count, 1, 0) != 1) {
+	if (!refcount_dec_if_one(&inode->i_count)) {
 		spin_unlock(&inode->i_lock);
 		return;
 	}
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1563,7 +1563,7 @@ xfs_itruncate_extents(
 	int			done = 0;
 
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
-	ASSERT(!atomic_read(&VFS_I(ip)->i_count) ||
+	ASSERT(!refcount_read(&VFS_I(ip)->i_count) ||
 	       xfs_isilocked(ip, XFS_IOLOCK_EXCL));
 	ASSERT(new_size <= XFS_ISIZE(ip));
 	ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -475,7 +475,7 @@ static inline void xfs_setup_existing_in
 
 #define IHOLD(ip) \
 do { \
-	ASSERT(atomic_read(&VFS_I(ip)->i_count) > 0) ; \
+	ASSERT(refcount_read(&VFS_I(ip)->i_count) > 0) ; \
 	ihold(VFS_I(ip)); \
 	trace_xfs_ihold(ip, _THIS_IP_); \
 } while (0)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -23,6 +23,7 @@
 #include <linux/fiemap.h>
 #include <linux/rculist_bl.h>
 #include <linux/atomic.h>
+#include <linux/refcount.h>
 #include <linux/shrinker.h>
 #include <linux/migrate_mode.h>
 #include <linux/uidgid.h>
@@ -622,7 +623,7 @@ struct inode {
 		struct rcu_head		i_rcu;
 	};
 	u64			i_version;
-	atomic_t		i_count;
+	refcount_t		i_count;
 	atomic_t		i_dio_count;
 	atomic_t		i_writecount;
 #ifdef CONFIG_IMA
@@ -2713,7 +2714,7 @@ extern unsigned int get_next_ino(void);
 
 static inline int i_count(struct inode *inode)
 {
-	int i_count = atomic_read(&inode->i_count);
+	int i_count = refcount_read(&inode->i_count);
 
 	/*
 	 * In order to preserve the 'old' usage-count semantics, remove the
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -676,7 +676,7 @@ get_futex_key(u32 __user *uaddr, int fsh
 		 * cases, therefore a successful atomic_inc return below will
 		 * guarantee that get_futex_key() will still imply smp_mb(); (B).
 		 */
-		if (WARN_ON_ONCE(!atomic_inc_not_zero(&inode->i_count))) {
+		if (WARN_ON_ONCE(!refcount_inc_not_zero(&inode->i_count))) {
 			rcu_read_unlock();
 			put_page(page);